The present invention relates to sample transport apparatus and, more particularly, to apparatus for circulating sample holders in a storage compartment past an operating station.
A prior art sample transport apparatus was disclosed in U.S. Pat. No. 3,859,528 issued to Luitwieler Jr. et al., issued Jan. 7, 1975 and assigned to Beckman Instruments, Inc., the assignee of the present invention. The prior art apparatus is designed for circulating a plurality of sample holder vials past an operating station. The vials are supported within holding trays which are circulated in rectilinear fashion in the sample storage compartment of the apparatus.
An elevator is provided at the operating station for removing a vial from the sample tray and positioning it in a radiation detection chamber for analysis, and then returning the vial to the sample tray in the compartment. A plurality of sample trays are contained in the storage compartment and grouped in two longitudinally extending, generally parallel columns on opposite sides of the operating station. Longitudinally movable fingers at opposite ends of each column move the entire column of trays incrementally, in a longitudinal direction, a distance of one tray depth to drive trays in the first column toward the operating station and trays in the second column away from the operating station. After moving each column of trays longitudinally, trays at the remote ends of the columns are indexed laterally from one column to the other after which the fingers again move the columns in increments of one tray depth.
Although the foregoing apparatus adequately performs its intended function, it does not possess certain advantages for which there is currently a demand. For example, as a result of the limited longitudinal drive capabilities of the incrementing fingers, incremental movement of each tray column requires that each tray abut an adjoining tray so that the trays can push each other serially in domino fashion.
The consequence of this arragement is that unless the apparatus contains a full load of trays, the incrementing finers will be unable to move the tray columns longitudinally to positions whereby the trays at the remote ends of the columns can be laterally indexed between columns. Also, when indexing, the apparatus may fail to accurately align a tray in position over the elevator at the operating station. In such a case, instead of engaging and removing the sample vial, the elevator will instead strike the tray and may jam the apparatus. In addition, there is no provision in the prior apparatus for detecting and correcting malfunctions of this kind.
There is, accordingly, need for sample transport apparatus having broader capabilities than those of the prior art. There is, for example, a need for apparatus which is capable of circulating sample holders of any number ranging from one to a full load and whereby a plurality of sample holder types, each adapted for carrying sample tubes of differing size and number can be freely mixed; and whereby jam-ups or stoppages of the transport apparatus are automatically detected and corrected.